Pulse intervals indicating device



y 1959' c. G. PL AURELL ET AL 2,888,559

1 PULSE INTERVALS INDICATING DEVICE Filed Feb. 21, 1955 I VVF/VToRS C424 620m: P404 Hum-v.4

.9774 [Ave NflAP/NG' QffOR/VE v f n. n l extr iu .t -:;cle. r.rninecl; :t'une intervals b w n themselvesmIERvALs INDICATING DEVICE 'Carl Georg -Paul Aurel], Stockholm, and Stig Erik Warring, :Hagersten, Sweden, .assignors to Telefonaktieholaget L Ericsson, Stockholm, Sweden, a corporation of Sweden Application February 21, 1955, Serial No. 489,658 Claims prigrity, application Sweden February 26, 1954 1 Claim. (Cl. 2 50-r27) 'fThezpresent invention. rel tes to a evi f r in t p1:es ence of two pulses with certain.

It is known to provide for this purpose a delay network, by which the first occurring pulse is delayed so much that it will occur at the same time as the following, which is then indicated in a suitable way. In the event that the time delays are small such system is fairly satisfactory, but when the time delays are long a delay network will be both bulky and considerably attenuate the applied signals.

The present invention provides another solution of the above mentioned problem without using a delay network, and the embodiment according to the invention is characterized by the first pulse causing a sinusoidal oscillation in a tuned circuit, the resonance frequency i of which is so chosen in relation to the time interval T between the trailing edge of the first pulse and the middle of the second pulse, that As a result the second pulse can be distinguished by its coincidence with the second half period of said sinusoidal oscillation, which is then rapidly attenuated.

An embodiment according to the invention comprises an electron tube with at least one control grid, one screen grid and one suppressor grid, the control grid and the suppressor grid having such bias voltages that they do not normally let any electrons pass, the screen grid and the suppressor grid being connected between themselves over a condenser and the screen grid being connected to its bias voltage source over an oscillating circuit, the resonance frequency f of which is so chosen in relation to the time interval T between the trailing edge of the first pulse and the middle of the second pulse, that The invention will be described more in detail in connection with the drawing, in which Fig. 1 shows an embodiment of a device according to the invention and Fig. 2 shows the voltage wave forms in some different points in the device.

In Fig. 1, 1 designates a pentode, the cathode of which is connected to ground 2 and the control grid of which is connected to an input terminal 3. The control grid and the suppressor grid 4 are each connected through separate resistances 5 and 6, respectively, to a bias voltage source 7 with negative polarity. The anode is connected through an anode resistance 8 to an anode voltage source 9 with positive polarity. The screen grid 10 of the tube is connected to the anode voltage source 9 through a parallel resonance circuit consisting of a coil 11 and a condenser 12. The screen grid is also connected to the cathode of a diode 13, the anode of which is connected to the anode voltage source through a second parallel resonance circuit consisting of a condenser 2,888,559 Paten e May 2.6, 1.85.?

, 2 14, .a coil 15 anda diode 16, the cathode of which is connected to the anode voltage source. The second resonance circuit is tuned to a lower frequency than resonance circuit 11, 12. The suppressor and screen grids of the tube are connected to each other through a con- .denser 17. The connection point between the anodes of the diodes 13 and16 are designated by 18.

The device operates in the following manner: Pulses of positive polarity are fed to the control grid. Said pulses cause the -flow of cathode current during their duration the negative bias voltage of the control grid be ing so high, that no cathode current can be obtained in the time, intervals between the. pulses. The input pulses .are shown in Fig. 2a and designated by 1923. When 16 for instancethe pulse .19 occurs, the negative bias voltage ofthe suppre ss or grid 4. is so high that, no anode, current isobtained, The whole cathode. current will thus flow to the screen grid 10 and feed energy to the oscillating circuit 11, 12 and also to the oscillating circuit 14, 15, the diode 13 being then conductive and the diode 16 blocked. During the duration of the pulse 19, the potential of the screen grid decreases and said voltage decrease is transmitted through the condenser 17 to the suppressor grid. When the pulse 19 ceases, the potential of the screen grid 10 will increase faster than the potential in point 18, since the oscillating circuit 11, 12 is tuned to a resonance frequency, higher, preferably three times higher than the resonance frequency of the oscillating circuit 14, 15. The diode 13 is blocked, so that the two oscillating circuits can oscillate each with its resonance frequency. Fig. 2b shows how the voltage V of the screen grid 10 and the voltage V in point 18, respectively, varies as a function of the time. The potential of the suppressor grid will follow the voltage variation of the screen grid 10, so that, when the pulse 20 is applied to the control grid, the suppressor grid has a higher potential than what corresponds to its cut-ofi voltage. The cathode current caused by the pulse 20 will therefore mainly flow to the anode, the screen grid only receiving its normal part of the cathode current. The pulse 20 will thus feed a rather small quantity of energy to the oscillating circuit 11, 12, and therefore the curve V in Fig. 2b is only somewhat flattened on the top. A pulse of negative polarity according to the curve V in Fig. 2c is obtained in the anode circuit, during the duration of the pulse 20. When the potential in point 18 is equal to the potential in point 9, the diode 16 will be conductive, so that the circuit 14, 15 is short circuited, and its energy is rapidly attenuated. About the same time the potential of the screen grid has decreased to the same value as the potential in point 9. The diode 13 is conductive, so that the circuit 11, 12 is short circuited by the diodes 13 and 16, and therefore the energy in this circuit is also rapidly attenuated. The potentials in the points 10 and 18 will thus follow the full diagram in Fig. 2b and not the dashed diagrams. When the next pulse 21 is applied to the control grid, the cycles will begin again. The time interval between the pulses 21 and 22 is, however, longer than the time interval between the pulses 19 and 20. The diodes 13 and 16 have therefore had time to be conductive and have attenuated the oscillations in the circuits 11, 12 and 14, 15, when the pulse 22 occurs. Thus, since the pulse 22 does not occur during the time interval, when the potential of the suppressor grid is higher than the cut-off voltage value owing to the oscillation in the circuit 11, 12, the pulse 22 cannot cause any anode current. For the same reason the next pulse 23 cannot either cause any anode current. Thus the pulse in Fig. 2c appears as an indication of the fact that only two pulses (19 and 20) with a certain determined time interval between themselves have occurred. 'As seen from Fig. 2b the time for of the oscillating period of the circuit 11, 12

corresponds to A of the oscillating period of the circuit 14, 15. The circuit 11, 12 should therefore be tuned' vice in the form of an electron tube having an anode,

I a cathode, a control grid, .a screen grid and a suppressor grid, a negative bias circuit including said control grid, said suppressor grid and a bias source having a potential at which said two grids normally block the flow of electrons, circuit means for feeding pulses of positive polarity to said control grid, a positive bias circuit ineluding a source of positive bias potential connected to 'said screen grid, a circuit including a coupling capacitor assaseo A a 4i r o connecting the suppressor grid to the screen grid, a first resonance circuit included in said positive=-bias-circuit, a second resonance circuit also included in said positive bias circuit, said second resonance circuit being tuned to a resonance frequency equal to one third of the resonance frequency of said first resonance circuit, a first diode, said first and said second resonance circuits being connected in parallel with each other but separated by the first diode, the cathode of said diode beingconnected to the screen grid, and a second diode connected'inrparallel with said second resonance circuit, the anodes of said two diodes being interconnected. Y

References Cited in the file of this patent UNITED STATES PATENTS I 2,389,004 Schroeder -5-.. Nov. 13, 1945 2,431,577 Moore Nov. 25,1947 2,468,058 Grieg Apt-26', 1949 2,591,940 Hugenholtz' Apr. 8, "195? 2,717,992

Weintraub Sept. 13, 1955 

